Exam 3(Lect. 27-32)

Question 1

Which of the following would be characteristic of a highly evolved pathogen?
A. Incidence of infection 50%, mortality 95%
B. Incidence of infection 1 in 10,000, mortality 2%
C. Incidence of infection 100%, mortality 100%
D. Incidence of infection 1 in 10,000, mortality 90%
E. Incidence of infection 90%, mortality 1 in 1,000

Answer 1

Incidence of infection 90%, mortality 1 in 1,000

Question 2

What are “pathogenicity islands”?
A. Clusters of virulence factor genes that can be transmitted by horizontal gene transfer
B. Groups of pathogenic bacteria bound to M cells
C. Patches of membrane receptors to which pathogenic bacteria bind
D. Plasmids on which multiple antibiotic resistance genes are located
E. Endemic disease foci with high prevalence of a particular disease

Answer 2

Clusters of virulence factor genes that can be transmitted by horizontal gene transfer

Question 3

How do bacteria with Type III secretion systems (T3SS) typically enter host cells?
A. The T3SS pokes a hole in the host cell membrane through which the bacteria enter.
B. The T3SS kills the host cell, making it easier for the bacteria to enter.
C. The T3SS enhances binding to macrophages, which engulf the bacteria.
D. Effectors secreted through the T3SS cause the host cell to enfold the bacteria in
membrane ruffles.
E. They don’t. T3SS are for secreting exotoxins, not for entering host cells.

Answer 3

Effectors secreted through the T3SS cause the host cell to enfold the bacteria in
membrane ruffles.

Question 4

Which of the following is a method for bacteria to evade the host immune defenses?
A. They use flagella to move from cell to cell .
B. They have capsules to avoid phagocytosis.
C. They bind the C3b protein, stealing it from the host.
D. They block transport of iron, a major oxidant.
E. They bind the Fab arms of antibodies.

Answer 4

They have capsules to avoid phagocytosis.

Question 5

Several organisms (Staphylococcus, Pseudomonas, Enterococcus) cause disease in catheterized
patients much more frequently than in non-catheterized patients. What is the most important virulence
factor for these organisms?
A. Antiphagocytic capsule
B. Exotoxin production
C. Respiratory transmission
D. Intracellular spread via actin polymerization
E. Ability to form biofilms on the catheter

Answer 5

Ability to form biofilms on the catheter

Question 6

A male patient ingests a dose equal to the ID50 of E. coli that expresses the type P pilus. What
would be the most likely outcome?
A. Pneumonia
B. Diarrhea
C. Urinary tract infection
D. An induced autoimmune disease
E. No infection

Answer 6

No infection

Question 7

A pathogen that has evolved for a long time in the same environment as its host will exhibit which
of the following?
A. High prevalence and high mortality
B. High prevalence and low mortality
C. Low prevalence and high mortality
D. Low prevalence and low mortality
E. High incidence and low prevalence

Answer 7

High prevalence and low mortality

Question 8

Elderly patients on long-term oral penicillin therapy often acquire the infectious disease
pseudomembranous colitis, caused by Clostridium difficile. How does penicillin use affect the course
of this disease?
A. Penicillin kills native flora, allowing C. difficile to colonize.
B. Penicillin creates a “super” strain of C. difficile that is more infectious.
C. Penicillin triggers a hypersensitivity response in the patient.
D. Penicillin reduces the severity of the C. difficile infection.
E. Penicillin has no effect on the course of this disease.

Answer 8

Penicillin kills native flora, allowing C. difficile to colonize.

Question 9

Which of the mechanisms below can bacteria use to escape phagocytosis?
A. Enhanced motility to get away from phagocytes
B. Extra iron binding proteins
C. Production of lysins to lyse the phagocyte
D. Producing an IgG protease
E. Preventing cytokine secretion from T cells.

Answer 9

Production of lysins to lyse the phagocyte

Question 10

A pathogen that has recently emerged in a particular region of the world would be expected to
have which of the following epidemiological characteristics?
A. High virulence and low prevalence
B. Low infectious dose and low mortality
C. Low prevalence and high incidence
D. Low mortality and high prevalence
E. balanced pathogenicity

Answer 10

High virulence and low prevalence

Question 11

What is a major difference between an infection and an intoxication?
A. An infection is best treated by inducing active immunity in an ill patient.
B. An intoxication is best treated by passive immunization.
C. An intoxication usually results in disorientation and neural paralysis.
D. An infection is more acute than an intoxication.
E. The consequences of an intoxication are not as serious as those of an infection.

Answer 11

An intoxication is best treated by passive immunization.

Question 12

Many pathogenic bacteria have evolved a C5a peptidase. What is the function of this virulence
factor?
A. It reduces the host’s ability to recruit phagocytes to the site of infection.
B. It binds host antibodies and neutralizes them.
C. It prevents the use of the membrane attack complex by the complement system.
D. It allows the bacterium to survive inside macrophages.
E. It creates membrane ruffles that enhance bacterial uptake by host cells.

Answer 12

It reduces the host’s ability to recruit phagocytes to the site of infection.

Question 13

Which of the following is the best example of balanced pathogenicity?
A. an organism that causes acute respiratory disease that is rapidly fatal
B. a foodborne organism that causes septicemia
C. both bacteria and viruses can cause pneumonia
D. a virus that causes mild diarrhea and is spread fecal-oral with an ID50 of 20 organisms
E. a bacterium that causes an equal number of respiratory and skin diseases

Answer 13

a virus that causes mild diarrhea and is spread fecal-oral with an ID50 of 20 organisms

Question 14

The picture at right shows a bacterium (arrow) entering an epithelial cell. The elaborate structure
that surrounds the bacterium forms . . .
A. when the PAMP on the epithelial cell contacts the
TLR on the bacterium.
B. by extension of the bacterial cell envelope
C. as a defense mechanism to prevent the epithelial
cell from being infected
D. in response to a bacterial protein secreted by a
Type III secretory system
E. as the first step in the membrane fusion process.

Answer 14

in response to a bacterial protein secreted by a
Type III secretory system

Question 15

Neisseria gonorrhoeae (Ng) can bind a host’s C3b regulatory protein. Why does Ng do that?
A. to inactivate C3b when it binds to Ng
B. to recruit more C3b to bind to Ng
C. to enhance Ng’s uptake into the host cell
D. to avoid the immune response by coating Ng with “self” antigens
E. That’s how the body recognizes that Ng is a pathogen.

Answer 15

to inactivate C3b when it binds to Ng

Question 16

What is the function of the Staphylococcal protein A?
A. IgA protease
B. Fc receptor
C. adhesin
D. prevents phagosome / lysosome fusion
E. activates complement C5a

Answer 16

Fc receptor

Question 17

Which of the following would you expect to be the eventual outcome of an evolutionary selection
process in a pathogenic bacterium?
A. Its ID50 will change gradually from 102
bacteria to 106
bacteria.
B. It will lose the proteins at the tips of its adhesion pili.
C. It will increase the size of its genome as it acquires a broad metabolic capacity.
D. It will change from an acute infection to a chronic one.
E. It will acquire the ability to kill its host much more quickly.

Answer 17

It will change from an acute infection to a chronic one.

Question 18

Correctly order the following steps in the Shigella infection cycle.
A. M cell entry → macrophage entry → epithelial cell entry → actin polymerization
B. macrophage entry → actin polymerization → epithelial cell entry → bacteremia
C. M cell entry → actin polymerization → epithelial cell entry → macrophage entry
D. macrophage entry → bacteremia → toxin production → epithelial cell entry
E. epithelial cell entry → actin polymerization → macrophage entry → bacteremia

Answer 18

M cell entry → macrophage entry → epithelial cell entry → actin polymerization

Question 19

Which of the following would typically NOT be true of an attenuated organism?
A. It lacks one or more pathogenicity islands.
B. Its ID50 is very low.
C. It lacks adhesion pili.
D. It generally causes a sub-clinical infection.
E. You develop a strong immune response against it.

Answer 19

Its ID50 is very low.

Question 20

A microbiologist tells you that there is no model organism for the disease he is studying. What
does he mean by this?
A. The structure of the disease organism is difficult to represent with a model.
B. There is no single organism that causes the disease.
C. The disease is an intoxication rather than an infection.
D. He will have to rely on Koch’s postulates to study it.
E. The disease only affects humans.

Answer 20

The disease only affects humans.

Question 21

Which bacterial invasion and colonization (I/C) factor is correctly matched with its role in an
infection?
A. siderophore – steals iron from the eukaryotic host
B. fimbriae – injected into a host cell and damage its cytoskeleton
C. Type III effectors – prevent uptake of bacteria by host cells
D. coagulase – alters the membrane structure of eukaryotic host cells
E. IgA protease – allows a bacterium to cause bacteremia

Answer 21

siderophore – steals iron from the eukaryotic host

Question 22

How are bacterial type III secretion system effectors involved in causing disease?
A. They rearrange the host cytoskeleton and allow the bacterium to enter host cells.
B. They allow the bacterium to compete with the host for binding iron.
C. They are leukocidins that the bacterium uses to kill phagocytes.
D. They mimic “cancel kill” signals so NK cells don’t kill infected host cells.
E. They bind to host cell receptors and are internalized like toxins.

Answer 22

They rearrange the host cytoskeleton and allow the bacterium to enter host cells.

Question 23

What are “pathogenicity islands”?
A. Patches of membrane receptors to which pathogenic bacteria bind
B. Plasmids on which multiple antibiotic resistance genes are located
C. Clusters of virulence factor genes that can be transmitted by horizontal gene transfer
D. Groups of pathogenic bacteria bound to M cells
E. Endemic disease foci with high prevalence of a particular disease

Answer 23

Clusters of virulence factor genes that can be transmitted by horizontal gene transfer

Question 24

At the right is a photomicrograph showing the bacterium Listeria monocytogenes (Lm) infecting a
human cell. What can you conclude about how this bacterium lives in its host?
A. Lm must have an M-protein on its surface.
B. Lm grows into long, filamentous cells once it is inside its host.
C. After it passes through MALT tissue, Lm invades the epithelial
basal membrane.
D. Lm probably has an antiphagocytic capsule.
E. Lm is able to use actin from its host to avoid humoral immunity.

Answer 24

Lm is able to use actin from its host to avoid humoral immunity.

Question 25

In the past 130 years we have learned quite a bit about microbes. Some things we have learned
have required us to modify the system Robert Koch developed in 1880 to identify the causative agent
of a disease. Which of the following has NOT required such a modification?
A. The recognition that we can only culture about 1% of the bacteria we’ve discovered
B. The discovery of infections caused by biofilms involving several bacterial species
C. Realizing that some diseases are of an inflammatory rather than an infectious nature
D. Recognizing the concept of idiopathic cases of an infectious disease
E. The development of cell culture models to study disease processes at the cellular level

Answer 25

Realizing that some diseases are of an inflammatory rather than an infectious nature

Question 26

What are fimbriae?
A. Special pili with adhesive proteins at their tips
B. Cells in mucous membranes that uptake bacteria
C. A type of bacterial exotoxins
D. Bacterial proteins that bind iron in host blood serum
E. Dense polysaccharide fibers present in bacterial biofilms

Answer 26

Special pili with adhesive proteins at their tips

Question 27

The genes for which of the following would be LEAST likely to be located on a pathogenicity
island?
A. A Type III secretory system
B. A bacterial siderophore
C. A superantigen toxin
D. An I/C factor
E. LPS biosynthesis

Answer 27

LPS biosynthesis

Question 28

Which of the following is a mechanism that bacteria use to avoid the host’s immune response?
A. Bacteria digest IgG
B. Bacteria secrete iron
C. Bacteria induce autoimmmune reactions
D. Bacteria cover themselves with antibodies
E. Bacteria cover themselves with C3b

Answer 28

Bacteria cover themselves with antibodies

Question 29

You are testing antibiotics in a mouse model of a new bacterial disease. You have determined the
MIC for the antibiotics from an E-test, and administered each antibiotic to several mice at greater than
the MIC dose. But all the mice still die. Which of the following would be a logical conclusion from
the results of this experiment?
A. You should look for the production of a toxin by the new bacterium.
B. You shouldn’t have used an E-test to determine the MIC of the antibiotics.
C. This new disease is probably polymicrobial.
D. You should have administered the antibiotics at a dose less than the MIC, not more.
E. Animal models are not valid for study of human diseases.

Answer 29

You should look for the production of a toxin by the new bacterium.

Question 30

All of the following are important for bacterial survival in a host EXCEPT the ability to . . .
A. digest C5a
B. produce siderophores
C. bind complement regulatory protein
D. induce autoimmune antibodies
E. produce an Fc binding protein

Answer 30

induce autoimmune antibodies

Question 31

What do the structures in these two pictures have in common?
A. They are both parts of the same bacterial cell.
B. Both involve rearrangements of the host’s cytoskeletal proteins.
C. Both occur when a bacterial capsule is produced within a host cell.
D. Both are immune responses to the presence of a bacterium.
E. Both are ways that Shigella can enter macrophages.

Answer 31

Both involve rearrangements of the host’s cytoskeletal proteins.

Question 32

When we say that a patient has a “disseminated” bacterial infection, what can we assume?
A. It was transmitted in sexual secretions as an STI.
B. The patient has or has had bacteremia.
C. The patient is suffering from an autoimmune sequela.
D. The infection is transmitted by the airborne route.
E. It is an infection of the disseminate, an accessory part of the digestive system.

Answer 32

The patient has or has had bacteremia.

Question 33

Throughout the 20th century, we have had to modify Koch’s postulates as we learned more
about host-pathogen interactions. All of the following observations have required modification
of Koch’s postulates, EXCEPT . . .
A. Occasionally a disease does not have an identifiable cause.
B. Bacteria eventually evolve less virulence as hosts evolve more resistance.
C. Most bacteria cannot be cultured in laboratory media.
D. Some infections are caused by several bacteria growing together in a biofilm.
E. Some bacteria that cause human disease do not cause the same disease in animals.

Answer 33

Bacteria eventually evolve less virulence as hosts evolve more resistance.

Question 34

Shigella are intestinal bacteria that can break out of the phagosome. What strategy do they
use to infect a host?
A. Prevent opsonization with antibodies to avoid phagocytosis
B. Coat themselves with host proteins to resemble “self” cells
C. Use Type III effectors to enter the apical membrane of intestinal epithelial cells
D. Get into macrophages as quickly as possible through intestinal M-cells
E. Develop a large anti-phagocytic polysaccharide capsule

Answer 34

Get into macrophages as quickly as possible through intestinal M-cells

Question 35

Which of the following is a method for viruses to evade the host immune defenses?
A. They use the host’s cytoskeleton to spread intercellularly.
B. They inhibit their binding to cell surface receptors.
C. They produce an antiphagocytic lipid capsule.
D. They prevent recruitment of the MAC by the complement cascade
E. They produce their own “cancel kill” signal for NK cells.

Answer 35

They produce their own “cancel kill” signal for NK cells.

Question 36

Which of the following is true of endotoxin, but not of an exotoxin?
A. Endotoxin is a cytoplasmic protein.
B. Endotoxin has much higher toxocity.
C. Endotoxin stimulates interleukin release, which results in fever.
D. Endotoxin can be the target for a vaccine.
E. Diseases caused by endotoxin can rarely be treated with antibiotics.

Answer 36

Endotoxin stimulates interleukin release, which results in fever.

Question 37

Most of the really dangerous pathogenic fungi can do which of the following?
A. Get inhaled as mold spores and transition to yeast in the host’s body
B. Produce spores within the host’s body
C. Escape the immune system by living inside red blood cells
D. Produce endotoxin
E. Grow as yeast in an environmental reservoir outside the host

Answer 37

Get inhaled as mold spores and transition to yeast in the host’s body

Question 38

How does your body respond to the presence of a superantigen toxin?
A. By secreting lots of cytokines and mounting a massive inflammatory response
B. By producing many more antibodies than normal, causing hypersensitivity reactions
C. By recruiting the complement cascade to kill host cells as well as bacteria
D. By engulfing the toxin and disseminating it via the blood to the tissues
E. By destroying connective tissue, resulting in necrosis.

Answer 38

By secreting lots of cytokines and mounting a massive inflammatory response

Question 39

What is the function of the B part of A-B toxins?
A. It binds to and inhibits B cells.
B. It enters the host cell and damages host cell metabolism.
C. It binds to surface receptors on the host cell.
D. It causes the main symptoms of anthrax.
E. It inhibits phagosome-lysosome fusion.

Answer 39

It binds to surface receptors on the host cell.

Question 40

Which of the following is usually true of an exotoxin, but not true of endotoxin?
A. There is a serum binding protein that binds to it.
B. It is an integral part of the cell envelope
C. It is easily detected by the Limulus amoebocyte assay
D. It usually causes a fever
E. The genes encoding it can be passed among cells on a pathogenicity island.

Answer 40

The genes encoding it can be passed among cells on a pathogenicity island.

Question 41

How does a phospholipase toxin kill cells?
A. By preventing phospholipid synthesis
B. By removing the head groups, thus destroying the amphipathic nature of the
phospholipid
C. By adding ADP + ribose to stop protein synthesis
D. By preventing uptake via membrane fusion
E. By digesting fatty acids, causing the lipids to not pack together as well

Answer 41

By removing the head groups, thus destroying the amphipathic nature of the
phospholipid

Question 42

How does a superantigen toxin function?
A. It is a very strong antigen that provokes a massive antibody response.
B. It crosslinks the TCR of TH cells to MHC2 that is not presenting an antigen.
C. It crosslinks TH cells to B cells, thereby producing lots of antibodies.
D. It dissolves the material that holds cells together in tissues.
E. It adds ADP-ribose to a protein, thereby inactivating it and killing cells.

Answer 42

It crosslinks the TCR of TH cells to MHC2 that is not presenting an antigen.

Question 43

The bacterium Listeria monocytogenes can live in phagocytes by breaking down the phagolysosome
membrane. Which of the following toxins could help L. monocytogenes do this?
A. A hyaluronidase
B. A superantigen
C. Endotoxin
D. An AB toxin
E. A phospholipase

Answer 43

A phospholipase

Question 44

How is LPS toxic to humans?
A. It agglutinates a type of red blood cell, causing DIC.
B. It activates B cells even without antigen binding, causing massive antibody release.
C. It binds to cells in the hypothalamus, damaging them and causing fever.
D. It increases cAMP concentration, causing edema and cell death.
E. It binds strongly to macrophages, causing a response that can lead to hypovolemia.

Answer 44

It binds strongly to macrophages, causing a response that can lead to hypovolemia.

Question 45

What is the function of the A part of an AB toxin?
A. It binds to surface receptors on the host cell
B. It hydrolyzes the head group of phospholipids
C. It facilitates bacterial spread through a tissue and into the bloodstream
D. It activates large numbers of TH cells
E. It enters the cytoplasm and kills the host cell, often by altering cell metabolism

Answer 45

It enters the cytoplasm and kills the host cell, often by altering cell metabolism

Question 46

For which bacterial toxins have we found a pharmaceutical use to make anesthetics more readily
able to penetrate through skin and other tissues?
A. ADP-ribosylating A-B toxins
B. hemolysins
C. hyaluronidases
D. endotoxins
E. superantigen toxins

Answer 46

hyaluronidases

Question 47

One reason why a vaccine against malaria has proven difficult to design is that the malaria parasite
. . .
A. has no surface proteins
B. has a virus-like protective coating that prevents antibody binding
C. covers itself with host antigens
D. lives in red blood cells, where it can avoid both cellular and humoral immunity
E. can swim through a tissue, avoiding humoral immunity

Answer 47

lives in red blood cells, where it can avoid both cellular and humoral immunity

Question 48

How does production of phospholipase enhance bacterial survival inside macrophages?
A. It binds the Fc end of IgG, thereby disguising the bacterium as a “self” cell.
B. It oxidizes macrophage proteins and kills the macrophage.
C. It prevents C3b from binding to the bacterial surface and activating complement.
D. It digests the antibody that most commonly attacks bacteria inside macrophages.
E. It disrupts the phagosome membrane, allowing the bacterium to escape.

Answer 48

It disrupts the phagosome membrane, allowing the bacterium to escape.

Question 49

Diphtheria toxin is an AB toxin. What does this mean?
A. It can be detected by the limulus amoebocyte assay.
B. There can be no vaccine made against it.
C. There is a receptor for it on a host cell membrane.
D. Diphtheria is mainly an intracellular pathogen.
E. It binds to and alters the structure of antibodies.

Answer 49

There is a receptor for it on a host cell membrane.

Question 50

How do bacteria with Type III secretion systems (T3SS) typically enter host cells?
A. The T3SS pokes a hole in the host cell membrane through which the bacteria enter.
B. The T3SS kills the host cell, making it easier for the bacteria to enter.
C. The T3SS enhances binding to macrophages, which engulf the bacteria.
D. Effectors secreted through the T3SS cause the host cell to enfold the bacteria in
membrane ruffles.
E. They don’t. T3SS are for secreting exotoxins, not for entering host cells.

Answer 50

Effectors secreted through the T3SS cause the host cell to enfold the bacteria in
membrane ruffles.

Question 51

What is this diagram depicting?
A. The typical activation of a TH cell by a macrophage
B. The function of a superantigen toxin
C. The function of an AB toxin
D. The attachment of a bacterium to a T cell
E. The activity of Staphylococcal protein A

Answer 51

The function of a superantigen toxin

Question 52

Why do some viruses produce an analog of MHC1?
A. To stop NK cells from killing cells infected by the virus
B. So the viruses can bind to the MHC1 and be internalized more readily
C. To be able to present viral proteins more easily on the surface of the host cell
D. It is a viral toxin that initiates an autoimmune reaction in the host
E. To reduce the efficiency of interferon binding to neighboring cells

Answer 52

To stop NK cells from killing cells infected by the virus

Question 53

Which of the following statements is accurate when comparing Anthrax toxin to LPS?
A. LPS is more likely to be inactivated by heat or formalin.
B. LPS is probably more toxic per microgram than Anthrax toxin.
C. The genes for Anthrax toxin are more likely to be located on a plasmid.
D. LPS contains more protein components than Anthrax toxin.
E. Anthrax toxin is more likely to remain attached to the bacterial cell membrane.

Answer 53

The genes for Anthrax toxin are more likely to be located on a plasmid.

Question 54

The bacterium that causes necrotizing fasciitis produces a hyaluronidase toxin. This toxin gives an
advantage to the bacterium because it allows the bacterium to . . .
A. spread more rapidly between the cells in a tissue
B. avoid the humoral immune response
C. induce a huge cytokine response in the host
D. be internalized more quickly by host macrophages
E. break out of the phagolysosome

Answer 54

spread more rapidly between the cells in a tissue

Question 55

Some viruses like Papillomavirus encode an inhibitor of the eukaryotic protein p53. Why?
A. so that they can coat themselves with a “self” protein
B. so that they can prevent infected cells from undergoing apoptosis
C. to cancel the “kill” signal that NK cells recognize
D. to allow them to invade deep tissues beyond the skin
E. so that they can escape from the phagosome before it fuses with the lysosome

Answer 55

so that they can prevent infected cells from undergoing apoptosis

Question 56

During some viral infections, infected cells fuse to form___________because_____________.
A. giant cells ; these cells are easier for the immune system to recognize
B. granulomas ; infected macrophages continue to secrete cytokines
C. granulomas ; these “activated” cells have a more potent oxidative burst
D. syncytia ; it allows the virus to avoid serum antibodies
E. syncytia ; these fused cells cannot produce interferon

Answer 56

syncytia ; it allows the virus to avoid serum antibodies

Question 57

Why can’t we produce a successful vaccine against endotoxin?
A. Our immune response against it is too weak.
B. It can’t be inactivated because it isn’t a protein.
C. It resembles human host proteins too closely.
D. It enters host cells so quickly that antibodies never encounter it.
E. It is found on a plasmid, and can spread too rapidly through a bacterial population.

Answer 57

It can’t be inactivated because it isn’t a protein.

Question 58

For which type of bacterial toxin is there a medical use - to make anesthetics more readily able to
penetrate through skin and other tissues?
A. cAMP-producing A-B toxins
B. phospholipases
C. IgA proteases
D. hyaluronidases
E. superantigen toxins

Answer 58

hyaluronidases

Question 59

The malaria parasite has a particularly effective method of avoiding both humoral and cellular host
immune defenses. Which of the following is correct about this parasite?
A. It lives in red blood cells
B. It produces keratinase
C. It grows within and travels between host epithelial cells
D. It coats itself with host proteins so that it resembles “self”
E. It causes host cells to fuse into syncytia

Answer 59

It lives in red blood cells

Question 60

What would be the most effective way to protect a patient against bacterial endotoxin?
A. Vaccinate the patient with an endotoxoid vaccine.
B. Test to see if intravenous fluids given to the patient coagulate Limulus blood cells.
C. Autoclave all intravenous fluids that might be given to the patient.
D. Use a Western Blot to screen any intravenous fluids given to the patient.
E. Passively immunize the patient against bacterial endotoxin.

Answer 60

Test to see if intravenous fluids given to the patient coagulate Limulus blood cells.

Question 61

All of the following are characteristic of bacterial A-B toxins EXCEPT . . .
A. The A part can cause increased production of cAMP
B. Multiple B parts can bind to multiple receptors
C. The B part can be used to produce a toxoid vaccine
D. An “attenuated” bacterium might have a mutation in the A part
E. They hydrolyze the A part of phospholipids away from the B part

Answer 61

They hydrolyze the A part of phospholipids away from the B part

Question 62

Why is there not yet a vaccine directed against bacterial endotoxin?
A. There is no market for one, so no one has tried hard enough to produce it.
B. There are too many different varieties of endotoxin.
C. Endotoxin is also a self-antigen in humans.
D. Endotoxin does not produce a strong enough immune response.
E. Endotoxin cannot be inactivated to produce a toxoid.

Answer 62

Endotoxin cannot be inactivated to produce a toxoid.

Question 63

How does a bacterial A-B toxin work?
A. It digests the host’s cell membrane phospholipids.
B. The B part blocks protein synthesis; the A part activates cAMP production.
C. The B part binds to receptors; the A part enters the host cell.
D. The A part activates the B part, which then binds to host cells and kills them.
E. The B part protects the A part from attack by the host’s immune system.

Answer 63

The B part binds to receptors; the A part enters the host cell.

Question 64

How could you tell if a particular pathogen produced a superantigen toxin when it infected a
patient?
A. Look for complete clearing when the pathogen is grown on a Blood Agar plate.
B. Look for tissue damage in a patient. Only superantigen toxins can do that.
C. Look for the release of cytokines from TH cells that do not recognize the pathogen.
D. Look for a larger than normal antibody titer against the pathogen.
E. Look for symptoms of DIC. Any pathogen that causes DIC probably produces a
superantigen toxin.

Answer 64

Look for the release of cytokines from TH cells that do not recognize the pathogen.

Question 65

Viruses use all of the following strategies to avoid the immune system EXCEPT . . .
A. production of an IgA protease
B. production of an interferon repressor
C. formation of syncytia
D. inhibition of the tumor suppressor p53
E. reversing the MHC-I antigen presentation pathway

Answer 65

production of an IgA protease

Question 66

Can the structure shown at the right be toxic? If so, how? If not, why not?
A. Yes, the part labeled ‘A’ can combine with antibodies to create a
hypersensitivity reaction
B. Yes, the part labeled ‘B’ can bind to a protein that induces a
strong cytokine response from macrophages.
C. Yes, the whole structure can bridge the interaction between naive
TH cells and APCs
D. No, the structure as shown lacks the toxic portion, and can only
bind to receptors.
E. No, the structure is not bacterial and has nothing to do with a toxin.

Answer 66

Yes, the part labeled ‘B’ can bind to a protein that induces a
strong cytokine response from macrophages.

Question 67

Which of the following statements about AB toxins is accurate?
A. The B-part of the toxin can inhibit the function of B cells.
B. The A-part of the toxin can hydrolyze phospholipid head groups.
C. The B-part of the toxin can be used as a vaccine antigen.
D. They have a medical use to allow anesthetics to penetrate tissue better.
E. They are only produced by Gram positive bacteria.

Answer 67

The B-part of the toxin can be used as a vaccine antigen.

Question 68

. A naked virus, HPV, produces a protein called E6. Recalling what infection HPV causes,
how does the E6 protein contribute to the infection?
A. It prevents the action of the p53 tumor suppressor gene in the host.
B. It blocks the MHC-I antigen presentation pathway in the host.
C. It allows the virus to form syncytia between infected host cells.
D. It prevents activation of TH cells by acting like an analog of MHC-II.
E. It stimulates the action of NK cells, which cause the HPV skin lesions.

Answer 68

It prevents the action of the p53 tumor suppressor gene in the host.

Question 69

The malaria parasite spends most of the human part of its life cycle in red blood cells
(RBCs). What does this imply about the body’s response to the presence of this parasite?
A. Antibodies can’t bind to the parasite, but TC cells can still kill infected RBCs.
B. Infected RBCs can only be killed by NK cells.
C. The parasite can be neutralized by antibodies once the antibodies bind to RBCs.
D. The parasite is exposed to neither humoral nor cellular immune responses.
E. The parasite’s surface proteins resemble those of the host.

Answer 69

The parasite is exposed to neither humoral nor cellular immune responses.

Question 70

For a chronic disease that is transmitted poorly between hosts (e.g. HIV) . . .
A. prevalence would be only slightly higher than incidence
B. incidence would be only slightly higher than prevalence
C. prevalence would be MUCH higher than incidence
D. incidence would be MUCH higher than prevalence
E. incidence would always be very low in a population

Answer 70

prevalence would be MUCH higher than incidence

Question 71

Which of the following is an important difference between droplet transmission and aerosol
transmission of a disease?
A. Aerosol transmission is limited to hosts who come into direct contact.
B. Only aerosol transmission results in an epidemic disease.
C. Droplet transmission almost always occurs via fomites.
D. Droplet transmission rarely results in a common-source outbreak.
E. Aerosol transmission is almost exclusively for digestive system diseases.

Answer 71

Droplet transmission rarely results in a common-source outbreak.

Question 72

The most effective way to reduce the incidence of nosocomially spread infections is to . . .
A. Disinfect operating rooms better between surgeries
B. Use more antibiotics in hospitals
C. Fit HEPA filters in all patient rooms
D. Separate patients into wards, grouped by the disease they have.
E. Have health care workers wash their hands between each patient they touch.

Answer 72

Have health care workers wash their hands between each patient they touch.

Question 73

A newborn with a case of trachoma is an example of . . .
A. Vertical disease transmission
B. Horizontal disease transmission
C. An immunodeficiency disease
D. Seasonal disease incidence
E. An endemic disease focus

Answer 73

Vertical disease transmission

Question 74

A person has a Staphylococcal skin infection. Another person acquires the same infection by
sleeping on the same sheet as the first person. The sheet in this scenario serves as . . .
A. A vector
B. A reservoir
C. A fomite
D. A portal of entry
E. A host

Answer 74

A fomite

Question 75

An example of an emerging or re-emerging disease is . . .
A. Cholera in India
B. Coccidioidomycosis in New Mexico
C. the annual Influenza epidemic
D. Tuberculosis in Europe
E. Gonorrhea in the United States

Answer 75

Tuberculosis in Europe

Question 76

Which of the following requires the strictest isolation between an infected patient and a healthcare
worker?
A. Standard precautions
B. Airborne precautions
C. Droplet precautions
D. Contact precautions
E. Blood and body fluid precautions

Answer 76

Airborne precautions

Question 77

Who or what is a fomite?
A. A dried sputum droplet that can become aerosolized
B. An exotoxin secreted by Streptococcus
C. The first person to become ill during an epidemic
D. An inanimate object that spreads infection via indirect contact
E. An air-filled vacuole within macrophages where bacteria are stored before digestion

Answer 77

An inanimate object that spreads infection via indirect contact

Question 78

The most common nosocomial infections are . . .
A. respiratory infections due to Staphylococcus transmitted in aerosols
B. surgical site infections from improper skin disinfection before surgery
C. urinary tract infections from improperly disinfected catheters
D. bacteremias caused by extremely drug resistant bacterial strains
E. ear, nose and throat infections like sinusitis or otitis media

Answer 78

respiratory infections due to Staphylococcus transmitted in aerosols

Question 79

Which of the following isolation procedures commonly used in hospitals is the least rigorous (i.e.
requires the minimum use of additional protective barriers between patient and healthcare worker)?
A. Body substance precautions
B. Droplet precautions
C. Airborne precautions
D. Contact precautions
E. Sterile precautions

Answer 79

Body substance precautions

Question 80

In a recent mumps outbreak the case incidence rate over
time is recorded as shown (x-axis is in weeks). This is an
example of . . .
A. A common-source epidemic
B. Fecal-oral transmission
C. Delayed hypersensitivity
D. A person-to-person epidemic
E. An endemic disease

Answer 80

A person-to-person epidemic

Question 81

Which of the following is a major portal of entry, but not a major portal of exit?
A. Upper Respiratory Tract
B. Digestive Tract
C. Wounds
D. Vaginal Epithelial Cells
E. Unbroken Skin

Answer 81

Wounds

Question 82

The incidence of a particular disease was followed
for two years (graph at right). Which of the following is
the most reasonable statement about its epidemiology
based on the graph?
A. It is spread by respiratory droplets.
B. It is spread by a mechanical vector.
C. It probably spreads in a city’s water supply.
D. It is an emerging disease that is transmitted
by fleas.
E. It is foodborne and associated with peanut butter.

Answer 82

It is spread by a mechanical vector.

Question 83

The average monthly prevalence of a disease
in several countries for the period 2004-2008 is
shown in the table at right as cases per 100,000
people. What can you say about the disease?
A. There was an epidemic of it in Canada in 2005.
B. It is likely to become a worldwide pandemic in 2009.
C. It was an acute illness in the UK in 2006.
D. It is likely a chronic disease in the United States.
E. It is endemic in the United States.

Answer 83

It is endemic in the United States.

Question 84

In nursing, Standard Precautions are taken to prevent transmitting disease via the nurse. In
addition, there are Supplemental Precautions based on . . .
A. the age of the patient (infant, elderly, etc.)
B. the part of the body the nurse must come in contact with
C. the mode of transmission of the disease the patient has
D. the prevalence of the disease in a particular hospital
E. how frequently the nurse must come in contact with the patient

Answer 84

the mode of transmission of the disease the patient has

Question 85

A flight lands at O’Hare with a passenger who has a respiratory disease. A week later, there are
155 cases of the disease in Chicago. By the second week, there are 6,000 cases and an epidemiologist
is consulted. He would most likely consider this to be . . .
A. a propagated epidemic of an airborne disease
B. a person-to-person epidemic with multiple index cases
C. a common-source epidemic
D. an example of an emerging disease
E. a disease transmitted by respiratory droplets

Answer 85

a propagated epidemic of an airborne disease

Question 86

Anthrax spores can survive for many years in soil. Soil is a ______ for anthrax.
A. host
B. vector
C. reservoir
D. fomite
E. portal of entry

Answer 86

reservoir

Question 87

The incidence of a particular disease was followed for a year
(graph at right). Which of the following is the most reasonable
statement about its epidemiology?
A. It is likely spread by direct contact.
B. It is likely spread by a biological vector.
C. There was a pandemic of the disease in June.
D. Its prevalence is much higher than its incidence.
E. It appears to be foodborne or waterborne.

Answer 87

It is likely spread by a biological vector.

Question 88

All of the following factors would presumably be especially important in nosocomial disease
transmission EXCEPT . . .
A. ability of an organism to form biofilms
B. presence of R-plasmids
C. transmission by direct contact
D. prevalence of an organism in a zoonotic reservoir
E. airborne transmission

Answer 88

prevalence of an organism in a zoonotic reservoir

Question 89

Which of the following is LEAST likely to be a portal of exit for a disease organism?
A. Semen
B. Urine
C. Feces
D. Saliva
E. Sweat

Answer 89

Sweat

Question 90

One day, an ICP for a large hospital in Chicago recorded 43 cases of a particular infection in the
hospital, including visitors as well as patients. This infection is not endemic to the area. The following
day there were 12 new cases. No new cases were recorded after that. The most likely source of this
outbreak was . . .
A. a visitor to the hospital who did not wash his hands
B. a kitchen that prepared food for the patients and for the cafeteria
C. a new patient admitted to the hospital with this infection
D. a nurse or doctor who is an asymptomatic carrier for the disease
E. contaminated tap water from the city’s water treatment plant

Answer 90

a kitchen that prepared food for the patients and for the cafeteria

Question 91

In order to prevent nosocomial infections, it is important to know which infections are the most
common so we can focus our efforts where they will do the most good. Which of the following is (by
far) the most common nosocomial infection in the United States?
A. E. coli urinary tract infections from indwelling catheters
B. Pseudomonas respiratory tract infections from contaminated air ducts
C. Staphylococcal infections of wounds and surgical incisions
D. Streptococcal bacteremia from contaminated I.V. lines
E. Fungal skin infections from contact with contaminated surfaces

Answer 91

Pseudomonas respiratory tract infections from contaminated air ducts

Question 92

Which of the following is an example of vertical transmission of a disease?
A. Fourteen people on an airplane become ill when a sick passenger is allowed to fly.
B. A nurse with MRSA passes it to several babies in the neonatal ward of a hospital.
C. Second-graders get Norovirus when a lunch worker forgets to wash her hands.
D. Three children in a family all get a cold from their Mom.
E. An HIV-positive baby is born to a mother with AIDS.

Answer 92

An HIV-positive baby is born to a mother with AIDS.

Question 93

A particular disease has a high seasonal incidence in the United States during February. Which of
the following is probably true about this disease?
A. It is a chronic illness.
B. It is propagated as a common-source epidemic.
C. Its incidence in February may be high but its prevalence is still low.
D. It is spread through respiratory droplets.
E. It is transmitted by a vector.

Answer 93

It is spread through respiratory droplets.

Question 94

What does it mean for a disease to be a “notifiable” disease?
A. The signs and symptoms are so obvious that the disease can be diagnosed quickly.
B. The symptoms are so painful that you know right away when you get sick.
C. The disease is serious enough that each case must be reported to the authorities.
D. It is unusual enough that new cases are often reported in medical journals.
E. It spreads so quickly that new cases must be placed in quarantine.

Answer 94

The disease is serious enough that each case must be reported to the authorities.

Question 95

Which of the following organisms is NOT found more commonly in a nosocomial setting than as a
community-acquired disease?
A. Pseudomonas aeruginosa
B. Pasteurella multocida
C. Methicillin resistant Staph aureus
D. urinary tract Escherichia coli
E. Enterococcus faecalis (Group D Strep)

Answer 95

Pasteurella multocida

Question 96

An example of an emerging or re-emerging disease is . . .
A. Malaria in Africa
B. Histoplasmosis in Indiana
C. the annual Influenza epidemic
D. Lyme Disease in the United States
E. Polio in Europe

Answer 96

Lyme Disease in the United States

Question 97

A chronic disease with a seasonal incidence peak in the summer would most likely . . .
A. have a prevalence peak in the winter
B. be transmitted via respiratory droplets
C. be called an “emerging disease” every summer
D. be vector-borne, like Lyme Disease
E. have incidence greater than its prevalence by the end of the summer

Answer 97

be vector-borne, like Lyme Disease

Question 98

Which of the following best explains the trend in the incidence of infectious
diseases in the US since 1980?
A. Increased stringency of public health and sanitation laws
B. Many diseases evolving towards balanced pathogenicity
C. Presence of endemic diseases in certain parts of the country
D. Increased use of new, more effective vaccines
E. Increased use of antibiotics, especially in nosocomial settings

Answer 98

Increased use of antibiotics, especially in nosocomial settings

Question 99

When following certain supplemental precautions, not only the nurse, but the patient also must
wear a face mask. Such a patient is also usually in a negative pressure room. What are we trying to
prevent with these precautions?
A. Transmission of droplet-borne infections from the patient to the nurse
B. Spread of an airborne infection from the patient to others in the hospital
C. The patient getting a disease carried by visitors from outside the hospital
D. Droplet-borne transmission from the nurse to the patient
E. The nurse acting as a fomite to spread the disease to others in the hospital

Answer 99

Spread of an airborne infection from the patient to others in the hospital

Question 100

A new virus is discovered. It is airborne, has a reservoir in geese, has a high ID50 for humans, has
a segmented genome, and has not yet evolved balanced pathogenicity. Which part of this information
is good news, and why?
A. Its being airborne. You can avoid it by staying a meter away from other people.
B. The high ID50. At least it takes a lot of it to kill you.
C. Its not being a balanced pathogen. At least it has not yet evolved to become as deadly
as it could be.
D. Its segmented genome. That allows you to break it up more with a vaccine.
E. Its reservoir in geese. That makes it potentially easy to eradicate.

Answer 100

The high ID50. At least it takes a lot of it to kill you.

Question 101

Which of the following has been most responsible for the trend in infectious disease incidence
since 1980?
A. Increased availability of clean water in developing countries
B. More global travel for tourism and economic migration
C. Increased use of vaccines against a larger number of pathogens
D. The eradication of many pathogens from the world population
E. Failure to comply with electronic disease surveillance programs

Answer 101

More global travel for tourism and economic migration

Question 102

A stroke victim is admitted to a hospital’s intensive care unit and placed on a respiratory ventilator.
She develops pneumonia characterized by green sputum and a high fever. How did she most likely
acquire this infection?
A. By contact with the patient in the adjoining bed
B. From the unwashed hands of a health care worker
C. By formation of a biofilm on the ventilator tube
D. From bacteremia caused by a urinary catheter
E. She should have been on airborne precautions because of the stroke.

Answer 102

By formation of a biofilm on the ventilator tube

Question 103

Rotavirus is frequently transmitted in daycare centers. Recalling what this virus causes,
which of the following is the most likely route of transmission?
A. Foodborne
B. Vertical
C. Direct contact
D. Airborne
E. Fecal-oral

Answer 103

Fecal-oral

Question 104

In the last 50 years, deaths in the US due to infectious diseases have . . .
A. decreased dramatically
B. remained about the same each year
C. increased again for the last 30 years after initial decrease
D. mostly been prevented due to clean food and water laws and increased sanitation
E. mostly been prevented due to extensive and widespread use of antibiotics

Answer 104

increased again for the last 30 years after initial decrease

Question 105

Nosocomial transmission of diseases is typically prevented by all of the following EXCEPT
A. use of masks and gloves for all patients and health care workers
B. cohorting of nurses and patients
C. positive pressure in rooms, negative in halls and common areas
D. use of ethanol-based hand sanitizers
E. regularly changing catheters and I.V. lines

Answer 105

use of masks and gloves for all patients and health care workers

Question 106

Several infants in the neonatal ward of a hospital show symptoms including red, inflamed skin with
peeling of the epidermal layer. They are likely infected with . . .
A. Pseudomonas aeruginosa
B. Streptococcus pyogenes
C. Sporothrix schenckii
D. Staphylococcus aureus
E. Rubeola virus

Answer 106

Staphylococcus aureus

Question 107

A 30-year-old patient presents to a clinic with heart arrhythmia and joint pain. A few weeks
previously, while camping in the Maine woods, he had noticed an unusual rash “like a bulls’ eye” that
had gone away. How had he likely become infected?
A. by eating contaminated food
B. by the bite of a small tick
C. by drinking water contaminated with rodent urine
D. through skin puncture or abrasion
E. by inhaling fungal spores in an aerosol of dry leaves

Answer 107

by the bite of a small tick

Question 108

The causative agent of tetanus is an AB toxin. Which of the following is true about it?
A. The A part binds to neurons.
B. The B part binds to lung epithelial cells.
C. The A part inhibits release of a neuroinhibitor.
D. The B part ADP-ribosylates a host cell protein.
E. It can be inactivated with an antibiotic.

Answer 108

The A part inhibits release of a neuroinhibitor.

Question 109

Rubella (“German measles”) is most serious in . . .
A. fetuses
B. infants
C. teenagers
D. young adults
E. elderly adults

Answer 109

fetuses

Question 110

Which of the following is NOT true of the chickenpox virus?
A. It is very serious if acquired by a fetus.
B. It can be spread even before the rash develops.
C. Once infected, the host retains the virus for her whole life.
D. There is an effective vaccine against it.
E. The spots in the rash all look the same a week after the onset of the disease.

Answer 110

The spots in the rash all look the same a week after the onset of the disease.

Question 111

Red skin rashes and white cheesy growth in moist areas of the body are caused by . . .
A. Candida albicans
B. Staphylococcus aureus
C. Corynebacterium diphtheriae
D. Bartonella henslae
E. Pseudomonas aeruginosa

Answer 111

Candida albicans

Question 112

What would be the most apparent way to distinguish rubeola from rubella?
A. Rubella is a respiratory disease
B. White spots are present in the lining of the mouth in cases of rubeola
C. Rubella has a much more prominent rash
D. Jaundice is present in cases of rubeola
E. Patients with rubella have a much higher fever

Answer 112

White spots are present in the lining of the mouth in cases of rubeola

Question 113

A major bacterial virulence factor that contributes to the condition
seen in the picture is . . .
A. An AB toxin
B. endotoxin
C. biofilm formation
D. production of an alternate “cancel kill” signal for NK cells
E. the enzyme coagulase

Answer 113

the enzyme coagulase

Question 114

Which of the following could best be described as an opportunistic pathogen with high levels of Rplasmid-mediated antibiotic resistance whose biofilms colonize patients with a weakened innate
immune system?
A. Streptococcus pyogenes
B. Clostridium tetani
C. Borrelia burgdorferi
D. Pseudomonas aeruginosa
E. Human Papillomavirus

Answer 114

Pseudomonas aeruginosa

Question 115

The Varicella-Zoster virus . . .
A. remains dormant in nerve tissue and re-erupts after many years.
B. may cause encephalitis and pneumonia in addition to swollen parotid glands.
C. is the main cause of genital herpes.
D. causes an infection that can be treated with tetracycline.
E. can form a granuloma and break out to spread to other organs

Answer 115

remains dormant in nerve tissue and re-erupts after many years.

Question 116

A patient developed a roughened circular patch of skin on his
face after playing with a cat. What infection would you suspect?
A. Sporotrichosis
B. Lyme disease
C. Cat-scratch fever
D. Coccioidomycosis
E. Ringworm

Answer 116

Ringworm

Question 117

Infection with Pseudomonas is best treated preventatively. It is very difficult to treat once an
infection has already occurred. Why?
A. It is Gram positive, but most antibiotics only treat Gram negative infections.
B. It is highly invasive, spreading throughout the body very rapidly.
C. It forms biofilms, which are very difficult to treat with antibiotics.
D. It lives inside macrophages, where antibiotics cannot penetrate.
E. They type of patients it infects are not able to tolerate most antibiotics.

Answer 117

it forms biofilms, which are very difficult to treat with antibiotics.

Question 118

A patient presents himself to a clinic in Connecticut with a concentric, “bulls’ eye” rash, muscle
aches and low-grade fever. What symptoms would likely be in this patient’s future?
A. Acute glomerulonephritis
B. Cirrhosis and liver cancer
C. Heart arrhythmia and joint pains
D. Disfiguring tissue granulomas
E. Tissue death and gangrene

Answer 118

Heart arrhythmia and joint pains

Question 119

A 9-year-old boy has a cough, fever, and runny nose. He also has a fine, macular rash and small
white spots in his mouth. What is the danger from this disease?
A. Damage to his T-cells may lead to serious secondary infections.
B. The rash might spread to internal organs, causing organ failure and DIC.
C. The causative virus is latent, and may recur later as a more serious disease.
D. Antibodies he makes against the causative bacterium might be responsible for
autoimmune sequelae.
E. If his mother is pregnant, his unborn sibling may develop congenital abnormalities.

Answer 119

Damage to his T-cells may lead to serious secondary infections.

Question 120

The Latin word tinea means “moth-like,” referring to the roughened patches of skin associated
with this type of disease. The disease is caused by a ______________ that has _____________ as one
of its main virulence factors.
A. bacterium ; an AB toxin
B. fungus ; dimorphism
C. virus ; syncytial formation
D. fungus ; keratinase
E. bacterium ; coagulase

Answer 120

fungus ; keratinase

Question 121

What do tetanus and gangrene have in common?
A. They are both caused by A-B neurotoxins.
B. They both require anaerobic conditions for the bacteria to grow.
C. They have very similar symptoms, including tissue necrosis.
D. Both are generally treated by amputation of the affected body part.
E. There is an effective vaccine for both of them.

Answer 121

They both require anaerobic conditions for the bacteria to grow.

Question 122

A wart such as the one shown at the right is caused by a . . .
A. virus
B. systemic fungus
C. dermatophytic fungus
D. spore-forming bacterium
E. protozoan

Answer 122

virus

Question 123

“German” Measles and Measles infections are mostly different, but there are some similarities.
Which of the following is similar between these two viruses?
A. They are both transmitted by respiratory droplets.
B. They both replicate in T cells, reducing the body’s ability to fight off other infections.
C. They are both associated with a congenital syndrome if they infect a fetus.
D. They are both in the same viral group (Rubella viruses).
E. Both are associated with small white spots at the site where the virus enters the body.

Answer 123

They are both transmitted by respiratory droplets.

Question 124

A baby develops a thick white growth in his mouth and on his
tongue. What microbial agent is probably responsible for this?
A. Papillomavirus
B. Staphylococcus aureus
C. Corynebacterium diphtheriae
D. Varicella-Zoster Virus
E. Candida albicans

Answer 124

Candida albicans

Question 125

A woman who had shaved only her lower legs all winter decided to shave
her thighs to prepare for summer. A few days later she developed small red
bumps all over her thighs. What is likely the cause?
A. Streptococcal erysipelas
B. Recurrence of Zoster from a previous Chickenpox infection
C. A shaving cut has become infected with necrotizing fasciitis.
D. Streptococcal or Staphylococcal impetigo
E. Staphylococcal folliculitis

Answer 125

Staphylococcal folliculitis

Question 126

Infections with which of these organisms are most associated with biofilm formation?
A. Staphylococcus aureus and Streptococcus pneumoniae
B. Streptococcus pneumoniae and Clostridium perfringens
C. Staphylococcus epidermidis and Pseudomonas aeruginosa
D. Pseudomonas aeruginosa and Streptococcus pneumoniae
E. Streptococcus pyogenes and Sporothrix schenckii

Answer 126

Staphylococcus epidermidis and Pseudomonas aeruginosa

Question 127

The most serious symptoms of Lyme disease are caused by . . .
A. antibodies made against the bacterium that causes the disease
B. a bacterial AB toxin that interferes with cAMP balance
C. production of gas in tissues, which cuts off the blood supply and causes ischemia
D. granuloma formation in the lung and other tissues
E. a hyaluronidase toxin that inhibits host cell protein synthesis

Answer 127

antibodies made against the bacterium that causes the disease

Question 128

The Latin word ‘tinea’ means “moth-like,” referring to the roughened
patches of skin associated with this type of disease. The disease is caused
by a ______________ that has _____________ as one of its main
virulence factors.
A. fungus ; keratinase
B. fungus ; dimorphism
C. virus ; IgA protease
D. bacterium ; an AB toxin
E. bacterium ; coagulase

Answer 128

fungus ; keratinase

Question 129

A 63-year-old man had a hip implant a year ago.
He has recently experienced pain in the hip, and
suddenly developed a high fever and septicemia. The
implant was removed, and its surface was scraped with
an inoculating loop and plated on Blood agar. The
growth is shown at the right. The organism most likely
responsible for the infection is _____________ and its
chief virulence factor is _____________.
A. Staphylococcus aureus ; beta hemolysis
B. Viridans group Streptococcus ; coagulase
C. Group A Streptococcus ; toxic shock syndrome toxin
D. Staphylococcus epidermidis ; ability to form biofilms
E. Clostridium perfringens ; an AB exotoxin

Answer 129

Staphylococcus epidermidis ; ability to form biofilms

Question 130

Which of the following disease organisms is correctly matched with the main symptoms of the
disease that it causes?
A. Pasteurella multocida – a circular or annular (“bull’s eye”) rash
B. Rubella – congenital syndrome with blindness, deafness and mental retardation
C. Varicella-Zoster Virus – cough, conjunctivitis and coryza (runny nose)
D. Bartonella henselae – spasms and rigid paralysis of all skeletal muscles
E. Hantavirus – painful blisters on the head or body of adults who have had chicken-pox

Answer 130

Rubella – congenital syndrome with blindness, deafness and mental retardation

Question 131

Which of the following statements about Human Papillomavirus (HPV) is correct?
A. Most HPV infections can eventually cause cancer.
B. HPV causes only some types of warts; other warts are caused by fungi.
C. The Gardasil vaccine is effective against all varieties of HPV.
D. Because it is protected by a tough envelope, HPV is difficult to destroy.
E. Only a few HPV types can insert their DNA as a provirus into the host’s chromosome.

Answer 131

Only a few HPV types can insert their DNA as a provirus into the host’s chromosome.

Question 132

The organism that produces the infection shown in the
picture has what major virulence factor?
A. a lipid envelope
B. dimorphic growth
C. ability to survive in macrophages
D. phospholipase
E. keratinase

Answer 132

keratinase

Question 133

Streptococcus and Staphylococcus infections can often resemble each other, but some are quite
distinct. Which of the following is exclusively a Staphylococcal disease?
A. Erysipelas
B. Impetigo
C. Furuncles
D. Intoxication with a superantigen toxin
E. Cat-Scratch Disease

Answer 133

Furuncles

Question 134

Tetanus and Gangrene are both diseases associated with traumatic tissue injuries. How are they
different?
A. They are caused by unrelated organisms.
B. Tetanus is an anaerobic infection; Gangrene is aerobic.
C. Tetanus causes tissue ischemia; Gangrene causes paralysis.
D. Tetanus can be treated with passive immunity; Gangrene can’t be.
E. Tetanus is much more common in the United States than Gangrene is.

Answer 134

Tetanus can be treated with passive immunity; Gangrene can’t be.

Question 135

A main virulence factor of both Staphylococcus and Pseudomonas is . . .
A. a green pigment that oxidizes macrophages
B. an IgA protease
C. a superantigen toxin
D. the ability to survive within phagocytes
E. the ability to form dense biofilms

Answer 135

the ability to form dense biofilms

Question 136

Your patient is an 8-year-old boy who has been bitten on the hand by a cat. He noticed a red area
around the bite site a few hours after it happened, but wasn’t concerned. A few hours after that, the red
area had begun to spread along his arm, and it really hurt, so he told his mom, who brought him to you.
You suspect that this is the same disease agent that causes respiratory distress diseases in livestock.
What is it?
A. Clostridium perfringens
B. Bartonella henselae
C. Pasteurella multocida
D. Clostridium tetani
E. It is likely an A-B intoxication, not an organism.

Answer 136

Pasteurella multocida

Question 137

All of the following diseases EXCEPT ___________ are more serious in the fetus because of the
fetus’s lack of cellular immunity.
A. Rubeola
B. Rubella
C. Varicella
D. Toxoplasma
E. Herpes

Answer 137

Rubeola

Question 138

One form of the organism that causes the symptoms
shown in the picture enters the body on the point of a
thorn. It then changes to another form and progressively
spreads along a lymphatic vessel. What is the disease?
A. Thrush
B. Coccidioidomycosis
C. Trichomonas
D. Sporotrichosis
E. Papillomavirus

Answer 138

Sporotrichosis

Question 139

Which of the following can be diagnosed by a characteristic rash and is usually transmitted to
humans by a biological vector?
A. Lyme Disease
B. Staphylococcal Scalded Skin Syndrome
C. Diphtheria
D. Sporotrichosis
E. Papillomavirus

Answer 139

Lyme Disease

Question 140

Which of the following is a childhood disease that is potentially serious because it leaves a patient
immunocompromised. It is now rare in the United States because of an effective vaccine.
A. Zoster
B. Group A Streptococcus
C. Measles
D. German Measles
E. Chickenpox

Answer 140

Measles

Question 141

The infant shown in this picture has an itchy red rash that is making him
fussy and irritated. The organism that is most likely causing this rash is . . .
A. a dimorphic fungus like Sporothrix
B. a yeast like Candida
C. a dermatophyte like ringworm
D. the Varicella virus
E. Bartonella henselae

Answer 141

a yeast like Candida

Question 142

Which of the following may appear in many places in the body, all of which usually involve
biofilms, often with a greenish pigment, forming on inadequately protected tissues?
A. Lyme Disease
B. Gangrene
C. Staphylococcus
D. Impetigo
E. Pseudomonas

Answer 142

Pseudomonas

Question 143

A 7-year-old girl went to the Doctor with a slight fever and swollen lymph nodes on her
upper arm and neck. She said she had been playing “dress up” with her cat 2 weeks ago, and the
cat didn’t like the game. Which of the following diagnoses was most likely?
A. Candida albicans
B. Bartonella henselae
C. Sporothrix schenckii
D. Epstein-Barr Virus
E. Pasteurella multocida

Answer 143

Bartonella henselae

Question 144

A person who developed the skin rash shown at
right might have what complication later on?
A. She might get a painful skin rash many
years later, because this is a latent virus.
B. She might get warts.
C. This virus can induce autoimmune kidney
sequelae.
D. If she is pregnant, her child may be born
with congenital Rubella syndrome.
E. The virus immunocompromses her, and she could get pneumonia or encephalitis.

Answer 144

She might get a painful skin rash many
years later, because this is a latent virus.

Question 145

What is a virulence factor of the organism that causes the dry, itchy,
contact-transmitted skin infection shown at the right?
A. An A-B toxin
B. An alpha-hemolysin
C. A tissue-specific adhesin
D. Keratinase
E. Ability to prevent phagosome-lysosome fusion

Answer 145

Keratinase

Question 146

What is usually the eventual cause of death in diphtheria patients?
A. Heart and kidney damage due to an AB cytotoxin that is absorbed in the blood.
B. Septicemia due to an invasive toxin.
C. Anemia due to iron binding by a bacterial siderophore.
D. Asphyxiation due to a pseudomembrane that blocks the tracheal opening.
E. Nephritis due to bacterial colonization in the kidneys.

Answer 146

Heart and kidney damage due to an AB cytotoxin that is absorbed in the blood.

Question 147

It is important to treat Strep throat aggressively as soon as it is noticed. Why?
A. It could develop into pneumonia if allowed to persist too long.
B. It could invade the throat tissues and cause necrosis.
C. Antibodies produced against it could damage heart valves and kidneys.
D. The longer it persists, the more likely you are to get it again.
E. The virus that causes it can also cause meningitis.

Answer 147

Antibodies produced against it could damage heart valves and kidneys.

Question 148

A common cause of both “pinkeye” and ear infections in children is . . .
A. Human Herpesvirus 1
B. Streptococcus pyogenes (Group A strep)
C. Haemophilus influenzae
D. Bordetella pertussis
E. Hantavirus

Answer 148

Haemophilus influenzae

Question 149

A 7-year-old child presents at a clinic with heartbeat abnormalities, a fever, and a whitish membrane
across the back of his throat. How should he be treated?
A. He should receive the DTaP vaccine.
B. He should receive antibiotics.
C. He should receive the antiviral medicine amantadine.
D. He should receive a passive IgG injection.
E. His symptoms should be treated, but there is nothing that can treat the disease.

Answer 149

He should receive a passive IgG injection.

Question 150

Upon looking at over-the-counter (OTC) medicines for “cold” and “cold with fever” you find that
the medicines are pretty much the same. What can you say about this, given your knowledge of the
organisms that cause these conditions?
A. They’re both rhinoviruses, so the treatment should be the same.
B. They’re very different viruses, but there is no specific treatment for either one.
C. The fever is probably a secondary bacterial infection, which can’t be treated OTC
anyway.
D. The treatment for “cold with fever” should be stronger to prevent the cold from
turning into Strep throat.
E. There shouldn’t be an OTC treatment for “cold with fever” - you need to see a Dr

Answer 150

They’re very different viruses, but there is no specific treatment for either one.

Question 151

A college student who was a cigarette smoker presented to a campus clinic with a high fever and a
hacking cough that had developed over the course of a few days. Extreme shortness of breath was
apparent. A sputum sample showed PMNLs and Gram positive cocci. The diagnosis would most
likely be . . .
A. Mycoplasmal pneumonia
B. Streptoccal pneumonia
C. Pertussis
D. Histoplasmosis
E. Tuberculosis

Answer 151

Streptoccal pneumonia

Question 152

Many of the organisms that cause eye infections also cause ear infections and sinusitis. There are
important exceptions, though. Organisms that cause eye infections but NOT ear ot sinus infections are
probably acquired . . .
A. via infected aerosols
B. from showering or bathing in infected water
C. by contact with infected respiratory droplets
D. during epidemics in the community
E. by direct or indirect contact with an infected source

Answer 152

by direct or indirect contact with an infected source

Question 153

Most of the time you don’t take antibiotics for a sinus infection; however, if you are a child and
have more than three cases of sinusitis caused by Haemophilus influenzae type b (Hib) within a few
months, a doctor will likely prescribe antibiotics. What is the concern that prompts antibiotic use in
this case?
A. Antibodies produced against Hib can also damage your kidneys.
B. Such prolonged sinusitis might develop into pneumonia.
C. Chronic Hib infections can cause ear damage, and can even lead to meningitis.
D. Antibiotics may be needed to disrupt the Hib biofilm that has formed in your lungs.
E. If the Hib infection is during flu season, the Dr is concerned that you’ll spread the flu.

Answer 153

Chronic Hib infections can cause ear damage, and can even lead to meningitis.

Question 154

Which of the following is NOT a morphological or physiological feature of the respiratory system
and associated organs that protects it against infection by pathogens?
A. ciliated epithelial cells
B. low pH
C. mucus secretion
D. lysozyme
E. native bacterial flora

Answer 154

low pH

Question 155

Sam has a bad cold, with a runny nose and fever. He has not been closer than 1 meter to other
people within the past week. Like 40% of students, Sam is not in the habit of washing his hands after
using the toilet. Which of the following is the most likely cause of his cold?
A. Streptococcus pneumoniae
B. Mycoplasma pneumoniae
C. Rhinovirus
D. Influenza virus
E. Adenovirus

Answer 155

Adenovirus

Question 156

The pathological structure indicated by the arrow in the throat of this 14-yearold immunocompetent patient is most likely caused by . . .
A. cytokine-induced inflammation in response to an infection
B. growth of a fungus on the tonsils of the patient
C. a bacterial AB toxin that is damaging throat epithelial cells
D. a virus that could have been prevented with the MMR vaccine
E. a Type II hypersensitivity response triggered by immune mimicry

Answer 156

a bacterial AB toxin that is damaging throat epithelial cells

Question 157

Haemophilus influenzae is a major cause of . . .
A. eye, ear, nose and throat infections and meningitis
B. lower respiratory tract infections in elderly adults
C. influenza pandemics
D. skin infections associated with severe acne in teenagers
E. mild “walking pneumonia” in young adults

Answer 157

eye, ear, nose and throat infections and meningitis

Question 158

The upper part of the healthy respiratory tract has a native flora, but the lower part is sterile. What
is mainly responsible for this?
A. the acidic pH at the back of the throat
B. ciliated epithelial cells that line the upper respiratory tract
C. the membranous folds of the vocal cords
D. IgA produced in the upper respiratory tract
E. rapid exhalation that expels organisms from the lungs

Answer 158

ciliated epithelial cells that line the upper respiratory tract

Question 159

Which of the following is a difference between rhinovirus and adenovirus?
A. One is a naked virus, the other is enveloped.
B. One causes colds, the other pneumonia.
C. One is spread via respiratory droplets, the other by direct contact.
D. One is acid-sensitive, the other can pass unharmed through the stomach.
E. There is an effective commercially available treatment for one, but not for the other.

Answer 159

One is acid-sensitive, the other can pass unharmed through the stomach.

Question 160

The major symptoms in a case of diphtheria are caused by . . .
A. the body’s immune response to the infection
B. growth of the bacterium across the tracheal opening
C. an AB toxin that interferes with protein synthesis
D. viral damage to the mucociliary escalator
E. a phospholipase toxin that lyses blood cells and steals their iron

Answer 160

an AB toxin that interferes with protein synthesis

Question 161

A patient has an upper respiratory infection caused by Haemophilus influenzae. It would not be
unusual if the patient developed __________ within the next week.
A. pneumonia
B. otitis media
C. endocarditis
D. flu
E. pertussis

Answer 161

otitis media

Question 162

What is pneumonia?
A. a bacterial infection that produces a toxin that damages lung epithelial cells
B. formation of lung granulomas in response to an infection
C. hemorrhage of blood into the lungs caused by septicemia
D. lung damage caused by an AB toxin that interferes with cAMP regulation
E. fluid secretion into the lungs as part of our immune response to an infection

Answer 162

fluid secretion into the lungs as part of our immune response to an infection

Question 163

The common cold is most frequently caused by . . .
A. Human rhinovirus
B. Corynebacterium
C. Group A Streptococcus
D. Varicella virus
E. Adenovirus

Answer 163

Human rhinovirus

Question 164

All of the following are true about diphtheria EXCEPT . . .
A. There is an effective vaccine against it.
B. Symptoms are caused by granuloma formation and cytokines.
C. It is spread person-to-person via respiratory droplets.
D. The expression of a key toxin is repressed by excess free iron.
E. Fatality is frequently due to heart damage as well as airway blockage.

Answer 164

Symptoms are caused by granuloma formation and cytokines.

Question 165

There are both 13-valent and 23-valent Pneumococcal vaccines. Which provides more effective
long-term protection, and why?
A. The 23-valent because it provides immunity against more strains of the bacterium
B. The 23-valent because it also provides immunity against the PMNs that cause
inflammatory damage.
C. The 23-valent because it has more electrons in its outer energy level
D. The 13-valent because it contains polysaccharide capsule antigens conjugated to
proteins
E. The 13-valent because it is a live attenuated vaccine rather than a subunit vaccine

Answer 165

The 13-valent because it contains polysaccharide capsule antigens conjugated to
proteins

Question 166

Which of the following is a common cause of otitis media in children, as well as an important
cause of more serious diseases such as meningitis and septicemia?
A. Adenovirus
B. Streptococcus pyogenes
C. Haemophilus influenzae
D. Rhinovirus
E. Neisseria meningitidis

Answer 166

Haemophilus influenzae

Question 167

Which of the following symptoms would be considered unusual in a case of Strep throat?
A. swollen lymph nodes
B. tonsillitis
C. red petechial patches in the throat
D. cough
E. pus production in the back of the throat

Answer 167

cough

Question 168

If you travel to the former Soviet Union and return with a case of Diphtheria, the Doctor will likely
give you a shot of Diphtheria Immune Globulin. What is that?
A. An antibody against a bacterial surface protein
B. An injected antibiotic
C. A toxoid vaccine
D. An active form of the diphtheria antigen
E. A passive antitoxin

Answer 168

A passive antitoxin

Question 169

Adenovirus is commonly cited as a way to deliver genes or drugs into human cells, because it
naturally infects our cells. Which 3 symptoms does this virus usually cause?
A. Conjunctivitis, cold and diarrhea
B. Sore throat, pyelonephritis and rheumatic fever
C. Pneumonia, diarrhea and vomiting
D. Cold, ear infection and meningitis
E. Diarrhea, pneumonia and warts

Answer 169

Conjunctivitis, cold and diarrhea

Question 170

A man returning from Russia developed a high fever with throat inflammation and a dirty
grey membrane across the back of his throat. The doctor told him that antibiotics wouldn’t help
much with this infection, but he gave the patient a shot anyway. Why?
A. A common co-infection can be treated with antibiotics.
B. The shot is a vaccine that can prevent further damage.
C. The infection might be Strep throat, which needs to be treated.
D. The shot is an immune globulin that can block the action of a toxin.
E. In case the doctor was wrong and antibiotics could help.

Answer 170

The shot is an immune globulin that can block the action of a toxin.

Question 171

Which of the following is transmitted more commonly as a community-acquired infection
than as a nosocomial infection?
A. Urinary tract infection due to E. coli
B. Otitis media due to Haemophilus influenzae
C. Scalded skin syndrome due to MRSA
D. Catheter-associated septicemia due to Enterococcus
E. Biofilm-associated Staphyloccus epidermidis infection

Answer 171

Otitis media due to Haemophilus influenzae

Question 172

After a visit from her 4-year-old granddaughter Sally, who had an ear infection, an elderly
nursing home resident, Mary, developed pneumonia. What would have been the most effective
way to prevent this infection?
A. Use of drainage tubes to reduce the severity of Sally’s ear infection
B. Sally should have been treated with penicillin
C. Mary should have been vaccinated with a 23-valent vaccine.
D. Since this is transmitted by direct contact, Mary should not have hugged Sally.
E. This is viral; nothing could have been done to prevent it.

Answer 172

Mary should have been vaccinated with a 23-valent vaccine.

Question 173

A frequent cause of the common cold, this acid-resistant virus can be transmitted by the
fecal-oral route as well as the respiratory route.
A. Influenza
B. Measles
C. Rhinovirus
D. Varicella
E. Adenovirus

Answer 173

Adenovirus

Question 174

A college student who was a cigarette smoker presented to a campus clinic with a high fever and a
hacking cough that had developed over the course of a few days. Extreme shortness of breath was
apparent. A sputum sample showed PMNLs and Gram positive cocci. The diagnosis would most
likely be . . .
A. Mycoplasmal pneumonia
B. Streptoccal pneumonia
C. Pertussis
D. Histoplasmosis
E. Tuberculosis

Answer 174

Streptoccal pneumonia

Question 175

A six-year-old girl has been brought to Urgent Care. She had had a fever and runny nose and then
had begun coughing. The coughs had become so severe that she began vomiting, and her mother was
afraid she couldn’t breathe. Which of the following vaccines could have prevented this disease?
A. an inactivated whole cell vaccine against Streptococcus
B. an attenuated live virus vaccine given as a nasal spray
C. a toxoid vaccine given orally
D. an acellular subunit vaccine conjugated to another vaccine
E. none - there is no vaccine against this disease

Answer 175

an acellular subunit vaccine conjugated to another vaccine

Question 176

An acute inflammatory respiratory disease associated with inhalation of aerosols from rodent urine,
and especially prevalent in the southwest US is . . .
A. Coccidioidomycosis
B. Histoplasmosis
C. Cryptosporidiosis
D. Hantavirus
E. Adenovirus

Answer 176

Hantavirus

Question 177

This organism forms two different types of spores - arthrospores in the environment, and
endospores in the host. There is a strong inflammatory response to the endospores, resulting in lung
and tissue granuloma formation. What is the organism?
A. Hantavirus
B. Bacillus anthracis
C. Histoplasma capsulatum
D. Pasteurella multocida
E. Coccidioides immitis

Answer 177

Coccidioides immitis

Question 178

A college student presented to a campus clinic with a low grade
fever and a cough that had developed over the course of a few
weeks. She said she felt tired. No lymph node swelling was
apparent. A chest X-ray is shown at right. A sputum sample was
stained, but no organisms were visible. The diagnosis would most
likely be . . .
A. Mycoplasmal pneumonia
B. Streptoccal pneumonia
C. Pertussis
D. Histoplasmosis
E. Tuberculosis

Answer 178

Mycoplasmal pneumonia

Question 179

The vaccine currently used to provide protection against whooping cough is . . .
A. A passive vaccine
B. A polysaccharide conjugate vaccine
C. An acellular subunit vaccine
D. A live attenuated vaccine
E. A whole-cell inactivated vaccine

Answer 179

An acellular subunit vaccine

Question 180

Which of the following is NOT associated with tuberculosis?
A. bone and liver granulomas
B. survival of the organism in macrophages
C. vertical transmission
D. lung necrosis
E. long-term treatment with multiple antibiotics

Answer 180

vertical transmission

Question 181

A major difference between the injected influenza vaccine and the “FluMist” nasal spray is that . . .
A. “FluMist” doesn’t have to be changed as often to compensate for antigenic drift
B. the injected vaccine elicits mostly cellular immunity
C. the injected vaccine is much more effective, although it is harder to make
D. “FluMist” also blocks uncoating of the virus intracellularly
E. “FluMist” induces active IgA immunity in a major portal of entry for the virus

Answer 181

“FluMist” induces active IgA immunity in a major portal of entry for the virus

Question 182

The largest outbreak of this disease in history happened in Indianapolis in 1978 when the old
Riverside Amusement Park was torn down. The buildings and rides had been unused since 1970, and
had gathered a large volume of bird feces. Over 100,000 people were infected, 400 were hospitalized
for respiratory distress and 15 died of a granulomatous disease. What was it?
A. Influenza
B. Histoplasmosis
C. Coccidioidomycosis
D. Hantavirus
E. Tuberculosis

Answer 182

Histoplasmosis

Question 183

A homeless man develops a chronic cough. When it gets so bad
that he begins to cough up blood, he goes to a community clinic, where
the following X-ray is taken. What should be done for this patient?
A. DOT should be started while awaiting the results of a
PPD test.
B. He should be vaccinated or boosted with DTaP.
C. A rapid Strep antigen test should be done to identify
the cause of his pneumonia.
D. He should be started on an oral course of oseltamivir.
E. The large syncytia in his lungs should be removed
surgically.

Answer 183

DOT should be started while awaiting the results of a
PPD test.

Question 184

Antigenic drift in influenza virus is . . .
A. a major reason for worldwide pandemics
B. a reassortment of H and N proteins between two viruses that infect the same host
C. the mechanism whereby influenza spreads from person to person around the world
D. possible because the flu virus has a segmented genome
E. a minor change in the virus spike proteins caused by mutation of the RNA

Answer 184

a minor change in the virus spike proteins caused by mutation of the RNA

Question 185

This organism is associated with a frequently fatal respiratory syndrome with capillary leakage
leading to pulmonary edema. It is spread primarily in the southwest United States by inhalation of dust
aerosols contaminated with rodent urine or feces.
A. Adenovirus
B. Sin Nombre hantavirus
C. Tinea corporis
D. Histoplasma capsulatum
E. Bartonella henselae

Answer 185

Sin Nombre hantavirus

Question 186

The United States recently switched from the DPT vaccine with a DT booster to the DTaP vaccine
with a DTaP booster. What is one reason why this change was made?
A. DTaP is an oral vaccine rather than injected.
B. Many adults were found to lack immunity to pertussis, so it was added to the booster.
C. There was an alarming increase in the prevalence of Diphtheria in the US.
D. The ‘aP’ in the DTaP vaccine provides broader coverage than the ‘P’ in DPT.
E. The DTaP vaccine provides passive as well as active immunity.

Answer 186

Many adults were found to lack immunity to pertussis, so it was added to the booster.

Question 187

Antigenic drift is especially rapid in influenza virus because . . .
A. it has a segmented genome
B. it infects humans and pigs as well as birds
C. it uses RNA as its genetic material
D. it is spread via respiratory droplets
E. it has two surface proteins that can recombine

Answer 187

it uses RNA as its genetic material

Question 188

The most common cause of lower respiratory tract infections in young
children causes irritation to the bronchiole lining, with the characteristically
damaged cellular appearance seen at right. What is this disease?
A. Respiratory Syncytial Virus
B. Influenza A
C. Streptococcal pneumonia
D. Mycoplasmal tuberculosis
E. Coccidioidomycosis

Answer 188

Respiratory Syncytial Virus

Question 189

Which of the following is true with respect to tuberculosis?
A. DOT is a new antibiotic that has been approved for treatment of XDR-TB.
B. Fecal transmission is important in addition to respiratory droplet transmission.
C. Nowadays it is typically spread zoonotically to humans by dogs.
D. It can affect the bones and liver as well as the lungs.
E. It cannot be treated by antibiotics that target the cell wall.

Answer 189

It can affect the bones and liver as well as the lungs.

Question 190

Which of the following statements about antigenic shift is NOT true?
A. It is caused by the lack of proofreading by RNA polymerase.
B. It requires two influenza A viruses to infect the same host cell.
C. It requires the influenza virus to have a segmented genome.
D. It affects mainly the Hemagglutinin and Neuraminidase proteins.
E. It is the main reason for periodic worldwide flu pandemics

Answer 190

It is caused by the lack of proofreading by RNA polymerase.

Question 191

A 3-week-old infant was brought to the emergency room in respiratory
distress. Inflamed bronchioles were found when she was examined, and the
following cell structures were seen in a microscope slide prepared from
bronchiole epithelial cells. What is the most likely cause of her illness?
A. Coccidioidomycosis
B. Hantavirus pulmonary syndrome
C. Respiratory Syncytial Virus
D. Diphtheria
E. Whooping Cough

Answer 191

Respiratory Syncytial Virus

Question 192

Which of the following fungal diseases is NOT correctly matched with a risk factor?
A. Histoplasmosis – aerosolized bird droppings
B. Candidiasis – failure to be vaccinated against it
C. Sporotrichosis – puncture injuries by plant thorns
D. Coccidioidomycosis – immune system impairment (e.g. AIDS)
E. All diseases are correctly matched with risk factors.

Answer 192

Candidiasis – failure to be vaccinated against it

Question 193

What is primarily responsible for the current trend in Pertussis incidence in the USA?
A. A better vaccine that has fewer side effects
B. Spread of resistant forms of the virus that causes Pertussis
C. Adult immunity decreasing below the herd immunity threshold
D. Increased tourism to areas of the world where Pertussis is endemic
E. Requirement for college students to be vaccinated if they live in dormitories

Answer 193

Adult immunity decreasing below the herd immunity threshold

Question 194

Mycobacterium tuberculosis (Mtb) can prevent phagosome / lysosome fusion. Therefore . . .
A. it is very difficult for Mtb to spread person-to-person
B. Mtb must be treated with antibodies rather than with antibiotics
C. Mtb can activate macrophages without TH cell involvement
D. granulomas can form in some cases of Mtb infection
E. Mtb can cause liver damage in addition to damage elsewhere in the body

Answer 194

granulomas can form in some cases of Mtb infection

Question 195

Which of the following is a difference between antigenic DRIFT and antigenic SHIFT in influenza
viruses?
A. DRIFT is somewhat predictable, SHIFT is not.
B. SHIFT occurs because influenza virus RNA is not proofread.
C. DRIFT can only occur in pigs or humans.
D. SHIFT is responsible for the annual influenza outbreak.
E. DRIFT alters the H and N designation of the influenza virus.

Answer 195

DRIFT is somewhat predictable, SHIFT is not.

Question 196

How does Mycobacterium tuberculosis cause the formation of
the structure indicated in the X-ray at the right?
A. It hydrolyzes tissue and damages the lung.
B. It multiplies rapidly to form the large bacterial colony
seen in the X-ray.
C. It survives in macrophages, which continue to secrete
cytokines.
D. It produces a toxin that results in the formation of blood clots.
E. It forms syncytia, one of which is seen in the X-ray.

Answer 196

It survives in macrophages, which continue to secrete
cytokines.

Question 197

Which of the following statements about influenza is FALSE?
A. There is a live vaccine and an inactivated vaccine against it.
B. Tens of thousands of Americans die every year from it.
C. It has a high mutation rate and is constantly changing.
D. It only infects humans, so can potentially be eradicated.
E. There is the potential for a new vaccine that recognizes many varieties of it.

Answer 197

It only infects humans, so can potentially be eradicated.

Question 198

An 18-month-old child developed bronchiolitis, and his mother took him to a clinic. The Doctor
saw that he was in obvious respiratory distress, but told the mother that there was nothing that could be
done but to keep his airway moist and hope that he recovered. This was the second time the infant had
been affected by the same illness. It is most likely . . .
A. Hantavirus
B. Respiratory Syncytial Virus
C. Haemophilus influenzae
D. Pertussis
E. Cryptosporidium

Answer 198

Respiratory Syncytial Virus

Question 199

Histoplasmosis is very common in Indiana. Which of the following is the most likely way to be
infected with this illness?
A. Someone with Histoplasmosis coughs on you.
B. You sit on a thorn that is contaminated with Histoplasma spores.
C. You inhale dry dust that has been contaminated with rodent urine.
D. You eat food that has been contaminated by Histoplasma bacteria.
E. You tear down a shed that has a large accumulation of bird feces inside it.

Answer 199

You tear down a shed that has a large accumulation of bird feces inside it.

Question 200

A 20-year-old student developed a cough and mild fever of 4 weeks’ duration. The causative
organism attached to his lung epithelial cells and caused irritation by secreting H2O2. What is
unusual about this organism?
A. It has no cell wall.
B. It induces autoimmune sequelae.
C. It allows formation of syncytia.
D. It survives in macrophages and spreads throughout the body.
E. It has an RNA genome and so its surface proteins undergo mutational variation.

Answer 200

It has no cell wall.

Question 201

Which of the following is typical in cases of miliary tuberculosis, but not in other TB cases?
A. A Type IV hypersensitivity against TB proteins.
B. Unexplained weight loss and chronic fatigue.
C. Granuloma formation in the liver with eventual liver failure.
D. Requirement to treat for months with many different antibiotics.
E. Recruitment of lymphocytes and macrophages toward infected cells.

Answer 201

Granuloma formation in the liver with eventual liver failure.

Question 202

Antigenic shift in influenza virus . . .
A. happens every year
B. happens because influenza has a segmented genome
C. is predictable for vaccine manufacture
D. happens because the influenza genome is not proofread
E. occurs only when influenza infects human

Answer 202

happens because influenza has a segmented genome

Question 203

The most common cause of viral pneumonia in young children is . . .
A. Rubeola
B. Hantavirus
C. Influenza
D. Respiratory Syncytial Virus
E. Rubella

Answer 203

Respiratory Syncytial Virus